A Sustainable Biosolids Drying Process

The Kent County Regional Wastewater Treatment Facility (KCRWTF) established a Sustainability Management System (SMS) in 2009. The SMS set an objective to begin moving away from dependency on fossil fuels due to their cost and negative environmental impact. The plant has long used a three-step process for treating their sludge production. In the first step, sludge is dewatered using one of three belt filter presses. The second step is to stabilize the biosolids through lime stabilization. The final step in the process is to dry the stabilized biosolids to approximately 50% solids using an indirect thermal dryer, where heat for the heat transfer fluid is provided from natural gas fired boilers and allows the biosolids product to meet the 40 CFR Part 503.32 limits under the time and temperature requirements. The resulting biosolids have been referred to as Kentorganite and been land applied as Class A biosolids on local farms. This paper looks at the results the plant has experienced from testing an alternative technology – the Parkson Thermo-System® Active Solar Sludge Dryer – to replace their lime stabilization and natural gas fired dryer processes and ultimately meet their sustainability goals.